There are various techniques for making multichamber tubular containers. The present invention is directed to multichamber tubular containers where each chamber contacts the exterior wall of the tubular container and extends longitudinally from the nozzle exit to the base of the tubular container. This is in distinction to the "tube in a tube" containers where the different chambers are located concentrically. It has been found that the arrangement where each chamber is in contact with the tube wall, i.e. with the tube wall forming a part of each tubular chamber, provides for more control over the dispensing of the contents from the tubular container. There will be a more uniform dispensing of the contents of each chamber in this construction of a multichamber tubular container.
One problem that is encountered in the manufacture of these multichamber tubular containers is the bonding of the interior divider walls onto the wall of the tubular container. In one method the interior wall or walls are attached to the tube wall prior to the tube being formed by bonding the two longitudinal edges of the divider wall to the outer wall. In this technique the interior wall is overlayed onto the outer tubular container wall, each in a flat orientation. The two longitudinal edges of the interior divider wall then are bonded to the interior surface of the outer tubular container wall. Upon the longitudinal edges of the outer wall being bonded together to form a tubular container there is formed a tubular container with two chambers. This can be a three or more chamber tubular container if there are additional interior walls. A problem that arises in the formation of these tubular containers is the bond of the interior dividing walls to the outer tube wall. There must be a strong, leak proof seal, but yet, one where there is no marring or otherwise putting an imperfection in the exterior surface of the outer tubular wall. Any imperfections will cause a perceptible imperfection in the tube decoration. Such imperfections are not acceptable since they affect the impression of the product by the potential purchaser. The product appears to be damaged.
Various techniques were tried in order to get a strong seal of the interior divider walls to the inner surface of the outer tubular container wall. A conventional heat seal formed by a heated platen surface on the interior divider wall has the problem that the divider wall is susceptible to sticking to the heated platen surface. Likewise, ultrasonic sealing was found not to be effective to form strong seals since the thin inner divider wall is susceptible to damage during the application of ultrasonic energy. The only technique to be found to be highly effective to produce strong seals at commercially feasible speeds with no imperfection in the exterior surface of the outer wall is the use of a band sealing technique where the band in contact with the exterior surface of the outer wall is held at a lower temperature than the band that is in contact with the surface of the divider wall. This results in strong seals with no imperfections in the exterior surface of the outer wall.
Band sealers customarily have two rotating bands. One band contacts the exterior surface of one material to be bonded and the other band contacts the exterior surface of the other material. In the present instance the one material is the chamber divider wall and the other material is the outer tubular container wall. The bands can be a metallic, ceramic or a plastic material. Polytetrafluoroethylene (PTFE) coated woven fiberglass bands have been found to be very effective. PTFE is stable at elevated temperatures and has a very lubricous surface. It will not adhere to the materials into which it comes into contact. The present invention is directed to the use of a band sealer where the band that is in contact with the exterior surface of the outer wall is maintained at a reduced temperature. This technique solves the problem of producing strong seals at commercially feasible speeds with no imperfections in the exterior surface of the outer wall of the container.